The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
Thermal spraying a metal powder, droplets and other comminuted particles/material onto cylinder bores surfaces of an engine block is known in the art. The wear-resistant coatings on the cylinder bore surfaces enable the use of aluminum, instead of heavy cast iron, to form the engine blocks. During the thermal spraying process, a gun nozzle is stationed relatively close to the bore surface due to the restricted diameter of conventional cylinder bores and sprays the metal powder, droplets or comminuted particles at very high velocities onto the cylinder bore surface. The relatively wide and uncontrollable spray pattern may result in non-uniform coating on the cylinder bore surface. More specifically, if a particle departs from its intended surface of deposition, it may become entrained onto the cylinder bore coating and cause iron oxide formations which may be detrimental to engine performance.
On the other hand, a beneficial iron oxide material may be formed in the coating during the thermal spraying process. After the thermal spray process, the cylinder bores generally undergo other processes, such as boring, washing and honing. These processes are likely to remove the iron oxide material from the thermal-sprayed coating, leaving voids in the coating. A cylinder block with voids on cylinder bore surfaces has oil consumption and emission issues, and thus may be scrapped, thus leading to operational inefficiencies, repair/warranty issues, and increased costs.